This invention relates generally to communications networks that support internal use of session initiation protocol (SIP).
Various kinds of communications networks are known. Many traditional switch-based communications networks (such as many Public Switched Telephone Networks (PSTN)) utilize signaling system 7 (SS7) signaling protocol to effect their own internal messaging needs including the exchange of transaction capabilities application part (TCAP) information. TCAP information comprises a variety of value-added information items that are typically stored in a database and that relate to general or specific functionality of the network (including, for example, information to effect routing services and functionality such as toll-free calling, call-forwarding, local number portability, and so forth). Other networks, however, and particularly more modern networks that comprise a so-called soft switch, rely upon other internal signaling protocols such as, for example, SIP.
Protocols such as SS7 and SIP are not inherently compatible with one another. As a result, an SS7 network cannot directly communicate with an SIP network. Such network-to-network communications, however, are often nevertheless necessary. Such need arises in part due to the substantial legacy base of installed SS7 networks. Although SIP-based soft switch networks offer numerous advantages over more traditional SS7 networks, in many cases a newer SIP-compatible network is simply added into a communications fabric that already includes one or more SS7 networks.
Signaling gateways, such as SS7/SIP signaling gateways, exist to facilitate the intercoupling of such incompatible systems. To a large extent such signaling gateways are a useful and successful tool and permit, for example, the establishment and maintenance of a call that originates in a first network (such as an SIP network) and terminates in or otherwise passes through a second network (such as an SS7 network). Unfortunately, there are many transactions, including various kind of calls, that the simple connectivity offered by a signaling gateway does not sufficiently address. For example, an originating call in an SIP-based network that requires TCAP information as resides within a linked SS7 PSTN-based network presently does not have the benefit of ready access to such TCAP information notwithstanding the existence of a link between the two networks as effected via the signaling gateway. Without such information, call setup may be delayed or even ultimately frustrated.